The Parasite: Onchocerca volvulus
 
     
  Etymology  
 


Greek onkos: barb
Greek kerkos: tail
Latin volvere: to turn, to roll
(47)


O. volvulus microfilaria (50)

 
  Taxonomy  
  Kingdom Animalia    
Phylum Nematoda (Aschelminthes)  
Class Secernentea  
Order Spiruridia  
Superfamily Filaroidia  
Family Onchocercidae  
Genus Onchocerca  
Species volvulus  
(48, 49)
       
The Nematodes, or roundworms, are a phylum of nonsegmented, cylindrical worms covered by a tough protective covering or cuticle. They have a complete digestive tract and separate genders. Many are free living, not parasites. (7)
   
Morphology
 
Macrofilaria: The adult worms of onchocerca are whitish and wire like, less than .5mm in diameter. The females are much larger than the males, measuring up to 50cm whereas males are not more that 5cm long. The adult females lie coiled in the fibrous subcutaneous nodules. The males migrate in the subcutaneous tissues to the nodules for reproduction. (7)
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Microfilaria: the microfilaria actively migrate throughout the dermis and connective tissues. They are unsheathed and only about 150 to 350 µm long. (7)
(51)